Luteinizing hormone binding receptor sites, present in isolated plasma membrane of bovine corpus luteum, will be isolated and purified. The interaction of I125 LH with the receptor site will be analyzed and the physicochemical properties, as well as the nature of the receptor site, will be defined. Using the knowledge obtained from the study of the physical interaction of LH with its receptor site we will study the effect of steroids on the turnover of binding site present in luteal cells maintained in tissue culture and their effect on the LH effector system. The effect of an ovarian growth factor on the rate of division of luteal cells will be analyzed and compared to the effect of LH. This will, hopefully, result in resolving whether LH is only essential for maintaining those cells in the differentiated state or if it is also involved in control of growth of luteal cells. The effect of the ovarian growth on the ovary will be analyzed.